Reptile Decomposition: An Actualistic Study Using Argentine Tegus (Salvator merianae)

The study of decomposition and its effects on remains in both the modern and fossil record is a fundamental cornerstone for the fields of forensic anthropology, paleoanthropology, and zooarcheology. However, given the historical focus of these fields on mammalian decomposition, taphonomic studies of other vertebrate clades remain comparatively underexplored. Consequently, findings from mammalian studies are oftentimes uncritically applied to the taphonomic histories of non-mammalian taxa. Recent investigations into the seemingly-contradictory taphonomic histories of exceptionally preserved dinosaurian “mummies” have raised important questions regarding the influence of intrinsic biological differences between mammals and reptiles during decomposition. With the goal of replicating foundational mammalian taphonomic studies, we observed the natural decomposition of thirty Argentine tegus (Salvator merianae) over a year’s time period. Specimens were placed in an open-grid container in a wooded clearing that enabled free access to insects but prevented macrofaunal access to the remains. Regular observations and visits to the site were made to track the stages of decomposition, insect succession, skeletal disarticulation, and weathering patterns.

A year after placement, all specimens retained significant amounts of skin, ranging from long strips to entire skin envelopes, contradicting previous assumptions that mummification happens under rare and unusual circumstances, as well as the conventional wisdom that extensive skin preservation in fossil organisms must rely on rapid burial. This retained skin envelope also had downstream effects on the disarticulation and post-mortem posture of the carcasses, as the dermal husks kept the internal skeleton in articulation well into a year after placement without the need for burial. Intense maggot activity concentrated in the cranial openings during the early stages of decomposition allowed the unfused, reptilian skull bones in some specimens to disarticulate away from the carcass, departing significantly from the limbs-first model of mammalian disarticulation. The dehydration of retained skin also offers a potential explanation for the iconic “death pose” seen in many dinosaurian taxa. The results from this study suggest that fundamental anatomical differences can have a direct effect on the expression of decomposition patterns between vastly different vertebrate clades, and stress the need for considering clade-specific anatomy when applying actualistic data to paleontological datasets.